The present invention pertains to material for potting and encapsulating electronic circuits utilized in high acceleration and high thermal cycling environments. In high acceleration environments, it is essential to utilize a material which is light-weight and strong to prevent movement of any of the electronic parts. In the high thermal cycling environments it is essential that the material has a low coefficient of linear expansion, relatively low modulus of elasticity (ratio of unit stress to unit deformation), high compression strength and low embedmant stress. Other characteristics which must be considered include repairability, cure stresses and cure temperatures, flow of material, outgassing properties, etc.
In the prior art, it is well known to utilize solid resins and hollow glass microspheres for flotation purposes in water craft and the like. However, these solid resins must first be thoroughly mixed with a curing agent and then the microspheres must be intermixed with the catalyzed resin before it cures. It is extremely difficult to completely mix the resin and curing agent and then to mix the hollow glass spheres into the catalyzed resin so that each particle of resin is catalyzed by a particle of curing agent and each glass sphere is affixed to another glass sphere by a particle of catalyzed resin therebetween. If the entire mixture is not uniform and substantially homogeneous there will be a great variation in the physical characteristics thereof, not only between different batches of mixture but within a single batch.
These materials are not suitable for potting and encapsulating electronic circuits because the physical characteristics are unsuitable. For example, most known materials of this type have a cure temperature far in excess of that acceptable with electronic circuits, i.e., the electronic circuits will be practically ruined by the time the potting material is cured or the cure time is too long to be economically feasible.